Switch



Jan. 1, 1924 7 1,479,178

' A. 1.. HARVEY swmon Filed Sept. 11 1920 WITNESSES: NVENTOR TORNEY Patented Juliet, 1924.

UNITED S ATES PATENT ornca.

ALBERT L. HARVEY, OI WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE mBIC & KANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

swrrcn.

Application filed September 11, 1920. Serial No. 509,573.

To all whom it may concern:

Be it known that I, ALBERT L. HARVEY, a citizen of the United States, and a resident of Wilkinsbur in the county'of Allegheny and State of %ennsylvania, have invented a new and useful Improvement in Switches, of which the following is a specification.

My invention relates to switches and particularly to limit switches that are adapted for use in connection with motor-operatedwrench control systems. The object of my invention is to rovide a switch for automatically controlling the o eration of motor-o erated wrenches that s all be simple and ciiirable in construction and effective in operation.

The present practice in operating-machines, such as lathes, presses and other ma chines using chucks, is to open and close the jaws of a chuck by means of a hand-operated wrench. In machines having a number of chucks, considerable time is saved, in a series of different machining operations, by tightening orloosening the jaws of a chuck automaticall In or er to automaticall cause the driving motor to become ine ective, when the wrench has succeeded in ti htening the jaws of a chuck, some form 0 limit switch is necessary. According to my invention, I provide a limit switch, that is responsive to the torque exerted by a. driving motor, for automatically controlling the operation of the dr1ving motor. The limit switch comprises a pair of switches adapted to be alternately engaged by a trip arm, and a pivotally mounted arm that is actuated by a resiliently mounted worm. j

The mechanical connection between the driving motor and a tool comprises the aforementioned resiliently mountedworm, a wormwheel, and a pair of .5 rings. worm is mounted on a square s aft. Longitudinal movement of the worm is resisted by the'force of a pair of springs,

My invention may best be understood by reference to the accompanyin'g'drawmgs, 1n

which,

Fig. 1 is a side" elevationalview, shown artially in section, of the" apparatus em-t dying my invention.

2is aside elevational view of a mod-.

Thev

ification of a in Fig. 1.

Fig. 3 is a top plan view of a motor-operated wrench and apparatus connected thereto.

' Referring particularly to Fi s. 1 and 3, a

part of the apparatus shown motor 1 actuates a wrench 2 t rough a resiliently mounted worm 3, and a worm wheel 4. A limit switch 5, comprising a lever 6 that is pivotally mounted on a supporting member? and a trip arm 8, is actuated by a collar 9 that is rigidly secured to the worm 3. The arm 8 which is secured to the arm 6, alternately engages switch members 10 and 11 of switches 13 and 14 upon corresponding longitudinal movements of the resiliently mounted worm 3.

The switch 13 comprises stationary contact terminals 15 and 16, a movable conducting member 17 for bridging contact terminals 15 and 16, a spring. 18 for actuating the conducting member 17 into enga ement with contact terminals 15 and 16 an the switch member 10 to be engaged by the arm 8 upon a movement of the worm 3 in a direction toward the switch 13. Switch 14 is identical in construction with switch 13.

The switches 13 and 14 are secured, respectively, to the motor 1 and to a supporting member 19. The worm 3, which is adjustably mounted on a square shaft 20, is held in substantially a central position by the force of a pair of springs 21 and 22. The collar 9 is rlgidly secured to one end of the worm 3. The square shaft 20 is rigidly secured to the main motor shaft 23. The worm wheel 4 is mounted on a shaft 24 which, in turn, is supported by supporting members-7 and 25.

Referring particularly to Fig. 3, the wrench 2 engages a screw 26 for actuating a set of jaws 27 of a chuck 28. The wrench 2 is adjustably secured to the worm wheel shaft 24 by means of .a coupling 29 of well known form.

The motor 1, and the apparatus connected thereto, are mounted on a table 30 which is arm 31 of the base member 32 by means of a pin 33. The table 30 is supported at the a other end b a projecting arm 34. v

The chuc 28" may "be either. of the expanding or the contracting type"; A chuck of the expanding type is one in which the jaws move radially outwardly to clamp the work in the chuck. A contracting chuck is one in which the jaws move radially inwardly to clamp the work in the chuck.

The operation of the system is as follows:

Assuming the apparatus arranged as indicated in Figs. 1 and 3, with the wrench 2 engaging the actuating screw 26 of the contracting chuck 28, torque is exerted by the wrench that tends to close the'jaws of the chuck 28 on applying power to the motor 1. The torque exerted by the motor 1 on the wrench 2 causes force to be exerted on the worm 3. By reason of the fact thatthe force exerted by the springs 21 and 22 on the worm 3 is not suflicient to balance the driving thrust of the wrench 2, the worm 3 moves, for a contracting chuck, in a direction tending to compress the spring 21,

The extent of movement of the worm 3, relative to the worm shaft 20 is thus dependent on the relative difference between the force of the spring 21 and the driving thrustproduc'ed by the wrench 2. With a movement of the worm 3, there is a corresponding movement of the lever arm 6 and the arm 8. After a predetermined longitudinal movement of the worm 3, arm 8 is actuated into engagement with switch member 10 to break the electrical circuit controlling the operation of the motor 1.

In order to simplif'ymy invention, the usual control circuits employed in connection with my limit switch, forgoverning the operation of the main motor, have been omitted.

Assuming the chuck 27 to be of the expandmg type and the apparatus to be arranged as indicated in Fig. 3, worm 3 is actuated in the direction of spring 22 upon the operation of the motor 1 to tighten the jaws of the chuck 28. .With longitudinal movement of the worm 3, there 1S3. corresponding movement of the arm 8, with the result that the arm 8 engages the projecting member 11, thereby breaking the circuit controlling the operation of the driving motor 1 and stopping the motor.

Referring to Fig. 2, the structure here shown is a modification of the arrangement shown 1n Figs. 1 and 3 for controlling the motion of the resiliently mounted worm 3. In this arrangement, a longitudinal movement of the worm 3 in one direction is limited by a collar 35 rigidly secured to the shaft 20. Movement of worm 3 in the opposite direction is resisted by the force of the spring 21. The structural arrangement shown in Fig. 2 is used in connection with a contracting chuck.

The particular advantage of the arrangement shown in Fig. 2 over that of Fig. 1 resides in the fact that the motor 1 will not become ineffective if an extra heavy torque is required to loosen the jaws of the chuck. Referring to Fig. 1, assuming a contracting chuck, if an abnormal torque is required to loosen the jaws of the chuck,

the trip arm 8 is actuated into engagement,

with switch member 11 to break the electrical circuit of the driving motor.

In the arrangement shown in Fig. 2, movement of the worm 3 is resisted by the collar 35 upon an abnormal torque being exerted by the motor in loosening the jaws of the chuck. t

The particular advantage of the present invention resides not only in the resilient connection between the driving motor and the tool, but also in the provision of a limit switch that is responsive to the resilient connection, whereby the motor becomes inetfective upon its torque exceeding a predetermined value.

Of course, my invention is not to be limited to motor-operated wrenches, but may find various other applications as, for example, in connection with motor-operated valves. I desire, therefore, that only such limitations shall be imposed thereon as are indicated in the appended claims.

I claim as my invention:

Q 1. In a system of control, the combination with a driving motor and a shaft, of

means for operatively connecting said driv- 1n pi sing a worm, and a worm wheel and means responsive to a movement of said worm in either direction whereby the torque exerted by said shaft is limited to a predetermined value.

2. In a system of control, the combination with a driving motor, adriving-motor shaft and a second shaft, of means for operatively connecting said driving-motor shaft and said second shaft, said means comprising a worm adjustably mounted on said drivingmotor shaft and a worm wheel rigidly secured to said second shaft, and means responsive to a movement of said worm in either direction whereby the torque exerted by said second shaft is limited to a predetermined value.' 1

3. In a system of control, the combina tion with. a driving motor, a driving motor motor to said shaft, said means comshaft and a second shaft, of means for oper-' atively connecting said, first and second shafts, said means comprlsmg a worm adjustably mounted on said motor shaft, a pair of-springs tending to resist long1tud1- nal motion of said wormin either direction, a worm Wheel rigidly secured to said second shaft, a supporting arm, means comprising a lever pivotally mounted onsaid su orting arm and adapted to be actuate y a movement of said worm, a second arm secured to said lever; and a pair of swltches adapted to be'alternately engaged by cor-' responding longitudinal movements of said arm, whereby the torque exerted seclond shaft is limited to a predetermined va ne.

4. In a sistem of control for power-o rated wrenc es, the combination with a 'ving motor and a wrench, of means, comprising a resiliently mounted worm and a worm wheel, for operatively connecting said driving motor and said wrench, and means responsive to a movement of said resiliently mounted worm in either direction whereby the torque exerted by said shaft is limited to a iredetermmed' value.

5. n a em of control for power-o rated wre bysaid es, the'combination with a 'vmg motor, a shaft, a wrench, operatively connected thereto and a chuck, of means for operatively connectin said driving motor and said wrench, sai means comprising a movably mounted worm, a 'worm wheel, a pair of helical springs mounted at opposite ends of said worm and means responsive to a movement of said resiliently mounted worm in either direction whereby the torque exerted by said wrench is limited to a predetermined value for an opening or closing of said chuck.

In testimony whereof, I have hereunto subscribed my name this 7th day of September, 1920. a v

ALBERT L. HARVEY. 

